A review on the potential of polyhydroxyalkanoates production from oil-based substrates

Polyhydroxyalkanoate (PHA) is a type of polyesters produced in the form of accumulated intracellular granules by many microorganisms. It is viewed as an environmentally friendly bioproduct due to its biodegradability and biocompatibility. The production of the PHA using oil substrates such as waste oil and plant oil, has gained considerable attention due to the high product yield and lower substrate cost. Nevertheless, the PHA fermentation using oil substrate is complicated due to the heterogenous fatty acid composition, varied bio-accessibility and possible inhibitory effect on the bacterial culture. This review presents the current state-of-the-art of PHA production from oil-based substrates. This paper firstly discusses the technical details, such as the choice of bacteria strain and fermentation conditions, characteristic of the oil substrate as well as the PHA composition and application. Finally, the paper discusses the challenges and prospects for up-scaling towards a cleaner and effective bioprocess. From the literature review, depending on the cell culture and the type of PHA produced, the oil platform can have a PHA yield of 0.2-0.8 g PHA/g oil substrate, with PHA content mostly from 40 to 90% of the cell dry weight. There is an on-going search for more effective oil-utilising PHA producers and lower cost substrate for effective PHA production. The final application of the PHA polymer influences the treatment needed during downstream processing and its economic performance. PHA with different compositions exhibits varied decomposition behaviour under different conditions, requiring further insight towards its management towards a sustainable circular economy.